Religion and culture were equally important to people living in the medieval era. Religion was a way to connect people across national borders and language barriers, but it was also a reason to fight wars and destroy communities. In Crusader Kings 3, religion serves all these purposes.
To make sense of the differences between religions, Crusader Kings 3 gives each of them a set of tenets and doctrines, and it divides them between faiths, religions, and religious families. Players can create new faiths, reform old ones, convert themselves and their realms to new faiths, and otherwise take advantage of the complex faith system the game offers.
Faiths, Religions, and Families
Every character in the game has a personally held Faith. Most of the tenets, doctrines, holy sites, and other aspects of religious life are determined by a given Faith. Each Faith belongs to a Religion, and each Religion belongs to a Religious Family. What these higher levels do is determine how members of one faith feel about members of another.
As an example, Catholicism and Orthodoxy are both Faiths of the Christianity Religion. Christianity and Islam are both Religions in the Abrahamic Religious Family, and Abrahamic, Pagan, and Eastern are the three Religious Families in the game.
Religious Family | Same Religion | Same Family | Other Family |
|---|---|---|---|
Abrahamic | Hostile | Evil | Evil |
Pagan | Astray | Hostile | Evil |
Eastern | Astray | Astray | Hostile |
Here's what each acceptance level means:
- Righteous: No penalties, full intermarriage, can fabricate and usurp titles as if they were members of the same faith.
- Astray: -10 Opinion, -15 Popular Opinion, full intermarriage, can usurp titles as if they were members of the same faith.
- Hostile: -20 Opinion, -30 Popular Opinion, intermarriage penalties, can't usurp titles but can fight holy wars.
- Evil: -30 Opinion, -45 Popular Opinion, heavy intermarriage penalties, can't usurp titles but can fight holy wars.
Tenets, Virtues, and Doctrines
Players can check the details of each Faith by using the religion menu in the lower-left corner of the screen. This will bring up the player ruler's Faith by default, but players can check others by clicking "Other Faiths" in the upper-right corner of the Faith menu. Be sure to uncheck the "Only X Faiths" box to see all the Faiths in the game.
Each Faith has three Tenets that provide big, unique bonuses to every follower. For instance, one tenet of Catholicism is Armed Pilgrimages, which makes declaring holy wars 20 percent cheaper, the Head of Faith can declare a Great Holy War every 30 years once they unlock and Catholic Fervor is over 75, and Catholic characters get a special bonus when they complete a pilgrimage. Tenets can also change how a Faith views other Faiths.
Just under the Tenets is a list of Virtues and Sins. These are character Traits that followers of the religion consider positive or negative, and a character with a Virtuous Trait gets a bonus +10 Opinion from members of the faith, +1 Piety per month, and an extra +10 Opinion from Zealot vassals. A character with a Sinful Trait gets the exact same numbers as penalties. Each Faith has three Virtues and Sins that players can't change without modding the game, but certain Tenets can add to or change these lists.
Faiths also have several Doctrines that describe how members of a Faith organize both their religion and their society. These are divided between Main Doctrines, Marriage Doctrines, Crime Doctrines, Clergy Doctrines, and Special Doctrines. Some cultural Traditions overlap with Doctrines, in which case the Tradition overrides the Doctrine. This guide won't go into detail about every Doctrine, but players can check all the options by trying to create a new Faith.
Fervor and Heresies
Another essential stat for every Faith is Fervor, which goes from 0 to 100. Faiths with high Fervor are better at converting counties and characters to their beliefs, and Faiths with low Fervor are more likely to be converted. Also, Fervor must be at 75 or above for the Head of Faith to call a Great Holy War.
Fervor goes up naturally as time goes on, but the more widespread a Faith is the slower its Fervor will grow. Fervor can also go up or down by 10 points thanks to virtuous and scandalous priest events. Fervor also drops when a character of the Faith successfully completes a holy war: -1 for a county, -2 for a duchy, -5 for a kingdom, and -30 for a Great Holy War.
If Fervor drops below 40, there's a chance that a heresy will show up somewhere in the Faith's territory. This chance goes up as Fervor continues to go down. This heresy will belong to the same Religion as the parent Faith, or it'll have a Syncretism Tenet that matches the Religion. For instance, if Catholic Fervor drops to 0, Bogomilism could appear in a Catholic kingdom since it's a Christian Faith, or Mandeaism could appear since it's a Dualist Faith with the Christian Syncretism Tenet.
If a heresy appears or spreads to the player ruler's realm, the game will give players the choice to convert to the new heresy for free. This is a good opportunity for players who want to start declaring holy wars against their neighbors, because converting to a heresy that has no presence on the map is very expensive otherwise.
Holy Sites
Another feature each Faith has is a set of holy sites. These are baronies that members of the Faith consider important for one reason or another, and if a member of the Faith controls the holy site, every follower of the same Faith will get a special bonus. The Catholic holy sites are Jerusalem, Vaticano, Cologne, Canterbury, and Santiago, and so long as a Catholic ruler controls Rome all Catholic followers get +1 Stewardship and +10 percent to Development speed.
Holy sites are also potential destinations for pilgrimages. Some especially famous holy sites, like Jerusalem and Mecca, have unique text and events for when players visit. The rest have more generic events. Most Faiths have 5 holy sites, but Hindu faiths have 7 and the number can go up or down by using mods.
Conversion
Technically, player rulers can convert from any religion to any other religion in the game. The problem is how expensive this can get in terms of Piety. First, there's a starting Piety cost that depends on how different the new Faith's Doctrines and Tenets are. If there aren't many differences, the Faith exists on the map and is near the player ruler's realm, the ruler's spouse belongs to this religion, and the ruler has the Apostate perk, this cost will go down to a very reasonable number.
On the other hand, if the new Faith is very different, belongs to a different Religious Family, doesn't exist anywhere on the map, and is an unreformed Pagan religion, the cost will be astronomical. If players want a ruler with an unusual Pagan Faith like Era Zaharrak or Hellenism, their best bet is to create a ruler who follows that Faith at the start of the game.
Players can also forcibly convert (and be converted) by taking someone as a prisoner and demanding they convert as a condition of freedom. Unless a character has the Zealot trait, they'll usually agree. A ruler can also demand that a courtier or vassal convert, and a guardian has a chance of converting their ward to their religion during a child's education.
Creation and Reformation
One last thing players can do with Faith is create one of their own. At the bottom of the Faith menu, players will see a button labeled, "Create New X Faith." However, it will say "Reform the X Faith" if the player ruler currently follows an unreformed Pagan Faith.
Either way, pressing the button will call up a new menu where players can completely remake their Faith from the ground up. The new Faith will belong to the same Religion, keep the same starting Virtues and Sins, and keep the same Holy Sites, but almost everything else can change. Players can choose new Tenets and Doctrines and set a new name, description, color, and symbol for the Faith. Some Tenets are limited by Religion or by which Doctrines are active, so choose carefully.
Reforming a Pagan Faith is very similar. Players can change the Faith's Tenets, Doctrines, and color, but the name and symbol are set in stone. Players can also leave the Faith's beliefs alone and reform just to get rid of the "Unreformed" tag, which is a big help all on its own. However, reforming a Faith also requires that the reformer control at least 3 holy sites.
In either case, creating a new religion is about as expensive as converting to an existing religion, and often it's even more expensive because each new Tenet or Doctrine adds to the cost. In fact, unreformed Pagans get a big discount for converting to an organized Faith instead of reforming their own. Players also need a different Perk, Prophet, to get a discount on creating or reforming a Faith, and this discount isn't as big as Apostate's.
Crusader Kings 3 is available now on PC, PS5, and Xbox Series X/S.